The present invention relates to a method for the fabrication of an conductive optical transparency. More specifically, but without limitation, the present invention relates to the fabrication of a polymeric, conductive optical transparency system, especially for use in aircraft applications.
A transparency system is typically defined, but without limitation, as a system or apparatus that permits the passage of radiation. An optical transparency system is more specifically defined, but without limitation, as an optical system or apparatus that permits the transmittance of electromagnetic radiation in the visible wavelength range. In aircraft, a transparency system includes, but without limitation, canopies and windows. These systems must be highly durable and lightweight, specifically in military applications. Current U.S. Naval Aviation transparency systems are constructed of acrylic, polycarbonate or composites thereof, which often contain an imbedded conducting layer of either ultra thin gold or Indium Tin Oxide for electrostatic discharge protection and radar cross section reduction. The conducting layer needs to be ultra thin so as not to diminish the high optical transparency required in the canopy and/or window, as gold and Indium Tin Oxide are optical absorbers in bulk form. Typically, the transparency system is multilayered with numerous interfaces between unlike materials. Delamination (splitting into layers) frequently occurs at the metal film/polymer interfaces due to various environmental exposure effects while in service. This delaminated or debonded area acts as an optical scattering center, which degrades the optical transparency of the system. Delamination areas require costly repair or replacement of the aircraft transparency system (typically a canopy or a window). In the current state of the art, an Indium Tin Oxide thin film is applied to a polymeric substrate through a sputtering process. The resultant Indium Tin Oxide film is optically clear and conductive, but it must be further protected with a polymeric topcoat due to its poor environmental and abrasion resistance. The multiple interfaces between layers create areas of potential delamination that can lead to debond failures and subsequent degradation in optical transparency.
Thus, there is a need in the art to provide a method for fabrication of transparencies that incorporates the listed benefits without the limitations inherent in present methods.